This invention relates to a vibrator which may be attached to a seat, a bed, and the like and produces a sensible vibration synchronized With an electric signal which drives a speaker.
U.S. Pat. No. 4,495,638 discloses a vibrator of the type described in the present application. The conventional vibrator includes a casing, a cylinder, a coil wound around the cylinder, a magnetic pole having an annular gap of such a required breadth as to have the coil inserted thereinto so that the coil is out of contact with the magnetic pole, and an annular leaf spring. An outer-peripheral end of the annular leaf spring is fixed to an inner wall of the casing, while an inner-peripheral end of the annular leaf spring is fixed to an outer periphery of the magnetic pole. Thus, the magnetic pole is hung on the casing and the cylinder is fixed to the casing so that the coil is inserted into the annular gap without contacting with the magnetic pole.
With such a structure, when an electric signal flows to the coil, a magnetic interference generates between the magnetic pole and the coil to vibrate the casing, thereby giving a sensible vibration to a person sitting on a seat or a bed to which the case is attached .
In the conventional vibrator, the annular leaf spring is used to position the coil properly in the gap and support the magnetic pole to the casing in such a manner as to be displaceable just centrally.
According to this structure, the magnetic pole cannot almost displace radially. When current flows in the coil, generating a magnetic interference, a magnetic force acts on the pole in such a manner that the center of the annular gap corresponds to that of the coil, if a small difference occurs between the center of the coil and that of the annular gap. Thus, the load continue to act on the annular leaf spring radially. The reason is that the magnetic pole cannot substantially displace radially. This may lead to a metal fatigue of the annular leaf spring, so that the annular leaf spring comes to fail.
Further, the annular leaf spring is too rigid to convert the current signal to an effective vibration.